I vented the distributor years ago
You know, as I read this I'm almost remembering you doing this. It sucks to get old.

my guess is that it weighs 450-500 lbs with the drums on it.
Yes. You will notice the additional mass. But no more worries about bearings chewing through axles or spiders letting go.

With the 40 gallon tank in the truck on a trip we went on we went through like 3 states before we had to get gas.
Nice. That would probably be 5 states if you were here in the northeast!

We've only seen a couple of cracked manifolds. I know it's a problem for people but I believe the combination of in-town driving, relatively low average speed, and less than full load trips keeps the heat down. I've considered headers (those sure are purdy!) but the cost including shop time to install was fairly high compared to used manifolds and I really have to watch spending for projects like that. Most of our 5.7 buses are approaching end of life. If I get three more years out of the '99 and '00 models I'll be lucky. It's a shame to let them go because we're literally throwing them away. Local scrap yard gave me $300 for a complete one last week. Dually rear, 4L80EHD, running 5.7, 0411 ecm. Two weeks ago we sent one down with no engine, trans, or other parts and they gave me $200. If only I had a place to store component parts!!